What is Science?

-the organized body of knowledge about the Universe derived from observation and

experimentation carried out to determine the principals underlying what is being studied

Branches of Science

Natural science

Biological sciences Physical sciences Earth sciences

botany

zoology

anatomy

physics

chemistry

geology

meterologyvirology

Scientific Method

• Question why or how something happens

• Research Existing Data

• Form a hypothesis (expected answer)

• Experiment

• Collect data (information)

• Draw a conclusion

• Contemplate opportunities for future study

DATA

• Data must be collected to support or refute the hypothesis:

• Data may be

Quantitative: Numeric Quantity

Qualitative: Descriptive in nature

The Scientific Method allows science to be universal. Why?

• Language Barriers exists between countries (English Speakers vs. Non-English Speakers)

• Measurement Standards (distance can be measured in feet or meters )

• This standardization allows for scientists around the world to share ideas.

Setting up a valid experiment: Scientific Method Style

• Make an observation: Plants seem to grow best with a certain amount of moisture.

• State the question: How does water affect the growth of plants?

• Form a hypothesis: If I give a plant more water, then it will grow taller.

• Set up the experiment: One control group and one experimental group.

• Collect data: Record plant growth and water distribution and graph the data.

• Repeat: Redo the experiment to disprove results.

Variables in an experiment

• Independent variable: the portion of the experiment that the scientist actually controls or changes (the cause / the if) -always graphed on the x axis

• Dependent variable: the portion of the experiment that changes on its own (the effect / the then) – always graphed on the y axis

DependentVariable

Independent Variable

Y axis

X axis

Control GroupFull sun and 25*C

Experimental GroupFull sun and 25*C

A B C D

Plant water added daily growth A 10mL 0 cm

B 15mL 5 cm C 20mL 10 cmD 25 mL 15cm

Growth(cm)

Water added(mL)

0 5 10 15 20 25

15

10

5

0

Growth vs. Water for Plants

A graph of this shape supports the hypothesis that more water increases plant growth.

Growth(cm)

Water added(mL)

0 5 10 15 20 25

15

10

5

0

Growth vs. Water for Plants

A graph of this shape does not support the hypothesis that more water increases plant growth. You may have

over-watered the plant and it wilted.

Significant Figures

• the number of digits in a measurement that are known with certainty

___________________________________

• 4 Rules for finding significant figures

• Rules for Adding / Subtracting Sig Figs

• Rules for Multiplying / Dividing Sig Figs

Rule 1 for determining Significant Digits

• All non-zero numbers are significant 1.27m has 3 sig figs

2278s has 4 sig figs

98 feet has 2 sig figs

Rule 2 for determining Significant Digits

• Any zero that is between two non-zero numbers is significant. 105m has 3 sig figs

190003cm has 6 sig figs

2006 mi has 4 sig figs

Rule 3 for determining Significant Digits

• Any zero to the right of a decimal is significant.

23.30s has 4 sig figs

0.450m has 3 sig figs

29.000m has 5 sig figs

Rule 4 for determining Significant Digits

• A zero that has the sole purpose of placing a decimal is not significant.

20 m has 1 sig fig

200 mi has 1 sig fig

0.0092 m has 2 sig figs

Addition and Subtraction for Significant Digits

• With addition and subtraction, limit your answer to the number of decimal places held by the measurement containing the least number of decimal places.

2.50cm + 9.0 cm = 11.5 cm (not 11.50 cm)

1/100DecimalPlace

1/10Decimal

Place

1/10DecimalPlace

35.05g - 5.0g = 30.05g =30.1g

1/100

Decimal Place

1/10Decimal

Place

1/10Decimal

Place

Rounding: 0-4 = Round down

5-9 =Round up

Multiplication and Division for Significant Digits

• When multiplying or dividing measurements, your answer should contain the same of significant digts found in the measurement with the least number of significant digits.

3.0 cm X 2 cm = 6 cm2 (not 6.0 cm2)

2 sig figs 1 sig fig 1 sig fig

50.00 g / 2 moles = 25 g/mole = 30 g/mole

4 sig figs1 sig fig

2 sig figs

Answer must also have 1 sig fig

Accuracy vs. Precision

• Accuracy– The closeness of a

measurement to an accepted value.

• Precision– The closeness of

a group of measurements to each other.

2 of 3 are accurate.Accurate?No.

Very precise. 3 are grouped together.

Measurement Examples

• Accepted Value: 10.0 m

• Measurements: 10.0, 9.9, 10.0, 9.9– Good accuracy, Good precision

• Measurements: 11.4, 11.5, 11.5, 11.6– Poor accuracy, Good precision

• Measurements: 8.9, 11.9, 12.5, 9.2– Poor accuracy, Poor precision.

Percent Error

• How far your measurements are away from an accepted value.

• You generally want 10% error or less. This would be equivalent to making a 90 on a test.

• Formula:• % Error = | observed value – accepted value| X 100%

accepted value

Percent Error Example

• The actual density of steel is 7.8 g/cc. In lab you measure the density as 9.2 g/cc. What is the percent error of your measurement?

• % error = | 9.2 g/cc – 7.8 g/cc | = 0.179 7.8 g/cc

Convert this number to a % by multiplying it by 100.

0.179 X 100 = 17.9 % = 18 %

Follow sig fig rules to round.

Measurements

• The SI System (International System)– Based on the metric system, the powers of

10, and uses prefixes.– World-wide use.– Also known as the KMS system.

• Kilogram, meter, second

– Mass will be measured in kilograms with a triple beam balance.

– Length will be measured in meters using a ruler.– Time will be measured in seconds using a stopwatch.

Prefixes for the Metric System

kilo

hecto

deca

base

deci

centi

milli

1

.1

.01

.001

10

100

1000

1.) Move up or down depending upon conversion of units.2.) Count steps each way.

3.) k, h, da, d, c, m

Base units: gram, liter, meter,second

Conversion Example:

• Convert 256 cm to meters.

meter

decimeter

centimeter

millimeter

1. Start on centimeter2. Count steps to meter.

3. Move the decimal 2 places to the left.4.) 2.56 m

Scientific Notation

• A way to express very large or small numbers. • Formula:

Z X 10n

• Z is the mantissa. It is a number between 1 and 10. The number of significant figures is included in the mantissa.

• n is a power of 10 that represents the direction and number of spaces that the decimal is moved in order to arrive at the Z number.

• Positive n moves the decimal to the right. Negative n moves the decimal to the left.

Example

• Convert 207,000 to scientific notation.

2.07 X 105

• Convert 0.00101 to scientific notation.

1.01 X 10-3

1.) write down all sig figs2.) place decimal so the number is

between 1 and 103.) count placeholders and record them as an exponent

Relationship of Science and Technology

• Wheel of knowledge:

Scientific Theory vs. LawScientific Theory vs. Law

• A scientific law is simply an observation about A scientific law is simply an observation about nature: Ex: What goes up, must come down”nature: Ex: What goes up, must come down”

• A scientific theory is an explanation of an A scientific theory is an explanation of an observation. Ex. “The bending of space observation. Ex. “The bending of space causes gravitation”causes gravitation”

• Theories are:Theories are:

-Simple and clear-Simple and clear

-Testable-Testable

-Repeatable-Repeatable